Process for recovering carbon dioxide from a gas mixture



0ct. 15, 1935. c:A H. vosBuRGH PROCESS, FOR RECOVERING'CARBON DIOXIDE FROM A GAS MIXTURE Filed April 18, 1951 Patented Oct. 15.., 1935 PROCESS FOR RECOVERING CARBON DIOXIDE FROM A GAS MIXTURE Charles H. Vosburgh, Forest Hills, N. Y., assignor to Harry W. Cole, New York, N. Y.

Application April 18, 1931, Serial No. 531,157

4 Claims.

This invention relates to improvements in processes for recovering carbon dioxide from a gas mixture and particularly to a process for so raising the percentage of carbon dioxide in a low 5 percentage gas, that the gas so raised in percentage'of carbon dioxide may be suitable for 'many commercial uses. A

'I'he object of this invention is to provide a process by means of which a gas with varying 1e .amounts of carbon dioxide may be so treated that it may have a high percentage of carbon dioxide and while it is capable of being carried out in` connection with many different types of apparatus, I have shown only one type of apparatus for use in connection therewith.

In carrying out my invention the gas containing the carbon dioxide which is to be treated in accordance with my invention, may be produced in the burning of coal, coke or oil, in fermentation process, or any process in which carbon dioxide is given oii as a by-product.

The drawing is a diagrammatic'representation of an apparatus by which my novel process can be carried out.

l0 designates a conduit for the gas from which the CO2 is to be obtained. l! is a blower which passes the gas through the whole system. The gas rst passes through a scrubber l2 containing coke or other inert material, over which water flows to remove dust and to cool the gas. Then it iiows through a second scrubber I3 which also contains an inert material such as coke, over which flows a stream of soda solution to remove sulphur compounds. These scrubbers and other devices for cleaning the gas may be of any desired type and their type is not germane to my invention. The soda solution in the scrubber I3 absorbs a certain amount of carbon dioxide and forms sodium carbonate after which no more carbon dioxide will be taken up. Thereafter, the sodium bi-carbonate absorbs the sulphur compounds.

From the last scrubber'the gas passes through a conduit 20 in which is a valve 2i to a primary accumulator tower 22. is a perforated plate near the base of this tower which supports a mass 25 of dry material capable of selectively adsorbing CO2. Activated carbon obtained by heating `cocoanut shells is one of the materials whichwgas mixture into the iirst or primary accumulator 55 l are suitable for this purpose. A coil of pipe 25 is embedded in this mass. 26 is a steam supply pipe connected with the end of the coil and 21 is a valve for controlling the steam. 28 is a steam outlet. 29 isa drain valve in the bottom of tower '5 22 for draining off any water or other liquid which may settle there.

The gas from the top of tower 22 passes through a conduit 35 and valve 3| into the bottom of a secondary tower 32 having a perforated plate 33 1'() and containing a mass of adsorbent material 34 similar to that in tower 22 and having' embedded therein a pipe coil 35. 33 is the steam supply pipe for coil 35, 31 its control valve and 38 its exhaust. A drain valve 35 is in the bottom olf-i5 tower 32.

From the top of the secondary tower 32 thev gas is led through a conduit 50 and valve 4! to the bottom of a final accumulator tower 42 of smaller dimensions. This is provided with parts 3g similar to those in towers 22 and 32 and designated respectively by the numerals 43, 44, 45, 46, 4l, llt and 49.

.50 is a conduit leading from the top of tower 42 through a valve 5| to the atmosphere or to a 25 stack, if desired. 52 is a CO2 testing indicator or gauge connected with the conduit 50. 53 is a branch conduit leading from the conduit 50 to a gas holder 55. 55 is a valve in conduit 53. The outlet pipe from the gas holder is designated 3() by 56.

Before pointing out the other parts of the drawing, I will describe my process. As the gas vpasses through the towers 22, 32 and 42, the CO2 therein is removed and adsorbed in the activated 35 carbon in them. I make use of the known characteristic of this material, that it is capable of adsorbing many times its .own volume of CO2. Other gases which it is not vdesired to retain, pass off through the conduit 50. Hydrogen sulphide 40 and sulphur dioxide are even more readily adsorbed than is carbon dioxide in such material as that of the mass 25. Therefore, when the gas initially supplied to the apparatus contains such sulphur compounds, they must be removed 45 beforethe gas is led into theiirst tower 22.. This is done in the scrubber I3 by the usual absorption process. So, as in the case of the example given of the specified more readily adsorbed gases, where other gases more readily adsorbed 5p than carbon dioxide are initially present in substantial percentage in Ythe carbon dioxide containing gas mixture, such more readily adsorbed gasesmay be removed prior to the entry of the Aare allowed to escape through conduit 5u.

cally before.

tower, such as tower 22 of the illustrated apparatus. After the activated carbon in the three towers has adsorbed all the CO2 it is capable oi holding under the existing conditions of CO2 percentage or concentration in the gas mixture the valve 2i is closed and the gas from the scrubbers diverted through another course.

Then steam valve 21 is opened and steam at a pressure of about 125'pounds with a temperature of about 350 F. is passed through the co-il 25 in tower 22. The gas which has been accumulated in the mass 24 is driven oii by the heat thus generated and passes into towers 32 Vand 42 in which the adsorption of CO2 increases and more of the undesired gases are allowed to escape through the conduit 50.

After the gas has been driven out of tower 22, valve 3| is closed and steam passed through coil 35 to drive the gas out of the activated carbon in tower 32 into tower 42 in which the adsorption of CO2 increases and more of the undesired gases The proportion of CO2 in the gas in tower 32 is much higher than it was in the gas which had been in tower-22. Thereafter valve di is closed and the gas accumulated in tower d2, which is nearly pure CO2, is driven out by passing steam through its coil 45.

When the gas passing through conduit 5G from the last'tower 42 is CO2 of the required purity, aswill be indicated by the `gauge 52, valve 54 is opened and valve 5i closed. This permits the pure CO2 adsorbed in the last tower 42 to pass vinto the holder 55 from which it may be withdrawn at will through pipe 56.

The fact that the activated carbon will adsorb only a deiinite amount oi carbon dioxide from a gas mixture having a certain percentage of carbon dioxide therein, but will adsorb a greater amount of carbon'dioxide lgas rwhen the percentage of c arbon dioxide in the mixture is increased,

-would appear due to the probable establishment of an equilibrium between the amount of carbon 'dioxide adsorbed and the other gases inthe mixture. Hence, whenthe gas mixture surrounding the activated carbon particles contains a higher percentage of carbon dioxide, this equilibrium is disturbed and more carbon dioxide displaces the other gases that are less readily adsorbed than the carbon dioxide, and which were adsorbed with the carbon dioxide under the prior conditions, and a further adsorption of carbon dioxide gas by the activated carbon results.

When the valveZi is closed, valve 2 i A is opened to allow the gas from the scrubbers to pass through towers 22A, 32A and 42A, which are duplicates of towers 22, 32 and 62, where the CO2 is accumulated and from which it is expelled while the first towers are being heated, in the manner previously described. Thus the process is continuous.

One of the advantages of this'process is the low cost of installation required for its practice.

YAnother advantage is its eiilcieney and cheapness of operation which makes it adaptable for the recovery of CO2 from sources such as ordinary fiue gas, which could not be done economi- Moreover, the periodic heating of the carbon in the accumulator 'towers causes it to retain its activity almost indefinitely and it is 'so disposed that it may be reviviiied without rethis purpose.

' vWhile yI have described my inventionin some detail, I wish it to be' understood that many changes may be made therein without departing from its spirit and scope and I intend no limitations other than those imposed by the appended claims.

What I claim is:

1. A process oi recovering carbon dioxide from a gas mixture of carbon dioxide and gas less readily adsorbed than the carbon dioxide, including passing said gas mixture through a plurality of carbon dioxide adsorption material masses contained in interconnected serially arranged enclosed-spaces, respectively, and permitting the unadsorbed gas to escape; then consecutively expelling the` adsorbed gas from each mass and progressively forcing it through the following masses 'of the series for adsorption thereby, while allowing unadsorbed gas to escape, until carbon dioxide gas from the preceding masses is concentrated in the last mass of the series; and finally expelling the adsorbed carbon dioxide from said last mass and collecting the expelled carbon dioxide.

2. A process of recovering carbon dioxide by raising the percentage thereof in a gas mixture of carbon dioxide and a gas less readily adsorbed than the carbon dioxide, that includes; passing said gas through a plurality oi masses of dry material adapted to selectively adsorb carbon dioxide in a series or" interconnected enclosed spaces and permitting the unadsorbed gas to escape from said spaces; consecutively closing the gas inlet ends of said spaces and heating the masses therein consecutively to progressively expel adsorbed gas from each heated mass and force the same through the following masses of the series while allowing unadsorbed gas to escape from the spaces; and collecting gas, expelled by heating the last of said spaces, in a suitable gas holder.

3. A process of Vrecovering carbon dioxide by raising the percentage thereof in a gas mixture of carbon dioxide and gas less readily adsorbed than the carbon dioxide, that includes the steps of; passing said gas mixture through a plurality of carbon dioxide adsorption material masses contained in a series of interconnected enclosed spaces, respectively, until a desired adsorption oi carbon dioxide by said masses is attained, while permitting the unadsorbed gas to pass oil? from said spaces; shutting off the supply of said gas to the series of adsorption material enclosing spaces; then consecutively heating each of the "series of adsorption material masses progressively one after the other to expel adsorbed-gas from each mass as heated and force the expelled gas through the next remaining unheated masses 'for further selective carbon dioxide gas adsorption thereby, while allowing unadsorbed gas to escape from the said remaining spaces; then heating the last adsorption mass of the series to expel therefrom the adsorbed high percentage carbon dioxide gas collectively adsorbed therein; and collecting the gas of the desired percentage of carbon dioxide as expelled from said last mass of the series.

4. A process of recovering carbon dioxide from a gas mixture of carbon dioxide and gas less readily adsorbed than the carbon dioxide, including the steps of; passing said gas through a plurality of carbon dioxide adsorption material masses contained in a series of interconnected enclosed spaces, respectively, of which the last mass is smaller than the one preceding it; continuing passage of the gas through said masses while permitting unadsorbed gas to escape from the enclosing spaces, until the desired adsorption of carbon dioxide by the masses is attained; shutting off the supply of said gas to the series of mass enclosing spaces; then consecutively T, heating each of the series of adsorption masses progressively toward said smaller last mass of the series, one after the other to expel adsorbed gas from each mass and force it through the next remaining unheated masses of the series for 10 further selective carbon dioxide adsorption thereby, While allowing unadsorbed gas to escape from the enclosing spaces, until there is a concentration of the expelled adsorbed gas of the preceding masses adsorbed in the smaller last mass of the series; nally heating the last mass of the series to expel therefrom the high percentage carbon dioxide gas collectively adsorbed therein; and collecting the expelled gas in a suitable gas receptacle.

CHARLES H. VOSBURGH. 

